Polyimides are the class of polymers that have found uses in demanding electronics needs. These are thermally stable polymers that are often based on stiff aromatic backbones. They are a very interesting group of incredibly strong and astoundingly heat and chemical resistant polymers. Their strength, heat and chemical resistance are so great that these polymers often replace glass and metals, such as steel, in many demanding applications.
Polyimides have very high glass transition temperatures with typical values greater than 300°C. Another key benefit that is provided by polyimide-based flexible circuits is a low coefficient of thermal expansion (CTE). A high modulus that is provided by poyimide films is thought to be an economic advantage as it allows a design engineer the potential to obtain adequate stiffness with a 1-2 mil film as an alternative to using a thicker substrate. Performance demands of polyimide films as a dielectric substrate for flexible printed circuit applications continue to intensify.